Method and electrode for electric arc welding



Nov. 30, 1965 w. E. FREETH ETAL 3,221,136

METHOD AND ELECTRODE FOR ELECTRIC ARC WELDING Original Filed May 27,1957 Inventor w\LL\AN EARL FREETH ERIC TAHE'S H NTROSE H\TCHE'L.L

4M JWWAttorney United States Patent 3,221,136 METHOD AND ELECTRODE FORELECTRIC ARC WELDING William Earl Frceth, Kemsing, Sevenoaks, Kent, andEric James Montrose Mitchell, Wolverhampton, England, assignors to TheBritish Oxygen Company Limited, a British company Continuation ofabandoned applications Ser. Nos. 661,660 and 661,666, May 27, 1957. Thisapplication July 7, 1961, Ser. No. 123,950 Claims priority, applicationGreat Britain, May 29, 1956, 16,648/56 9 Claims. (Cl. 219146) Thepresent invention relates to methods and electrodes for electric arcwelding of ferrous materials, and this ap plication is a continuation ofour prior applications Serial No. 661,660 and Serial No. 661,666, eachfiled May 27, 1957, and both now abandoned.

In the welding of ferrous materials, electrodes having a core wiresurrounded by so-called flux coatings have been employed for many yearsand a Wide range of different coating composition has been used toprovide a range of electrodes, each essentially suitable for weldingspecific materials under specified conditions, not only of current butalso of position. Electrodes of the low hydrogen type having a coatingcomposition containing a high proportion of basic materials, such forexample as calcium fluoride have been found even at the high currentdensities used in automatic Welding to deposit weld metal having goodmechanical properties but such electrodes at high current densities havebeen found suitable only for welding in a substantially flat position.Additionally, when heavy deposits are made with such electrodes undernormal conditions in one or more passes porosity may result in thedeposited weld metal. On the other hand, electrodes having a coatingcontaining a high proportion of rutile materials have been found moresuitable for welding out of the fiat position, in thehorizontal/vertical fillet position for example, but unless the currentdensity is severely restricted it has been found that the mechanicalproperties of Weld metal laid down by such electrodes are relativelypoor.

It is an object of the present invention to overcome these disadvantagesof known arc welding methods using coated electrodes.

According to the broadest aspect of the present invention a method ofelectric arc welding ferrous material comprises establishing an electricare between a workpiece of said material and a coated electrode having acore of ferrous material provided with a bonded coating of low hydrogencontent containing fluxing material and deoxidising material, and inconjunction with the coated electrode supplying a gas consistingessentially of carbon dioxide to shield the arc and the welding zonefrom the atmosphere during welding, said coating acting as a barrierbetween the shielding gas and the core, and the materials of saidcoating functioning both to limit oxidation of the weld metal by theshielding gas and to produce a layer of slag on the deposited weldmetal.

Known low hydrogen type welding electrodes usually deposit weld metalhaving a diifusible hydrogen content of less than millilitres perhundred grams of weld metal, and usually of not more than one millilitreper hundred grams of weld metal. The electrode coatings in accordancewith the present invention preferably contain a suiticiently low levelof hydrogen to enable weld metal of this quality to be deposited.

By the term gas consisting essentially of carbon dioxide as used hereinis meant a gas containing at least 80% by volume of carbon dioxide.Carbon monoxide, gaseous hydrocarbons, nitrogen or monotomic gases suchmanufactured so as to contain a minimum of residual hy-' drogen, is usedin conjunction with a shield of carbon dioxide to exclude the atmospherefrom the welding zone, and to reduce the concentration of residualhydrogen in the arc, weld metal having good mechanical properties can bedeposited at high current density, and moreover, the welding position isnot restricted to welding in a horizontal plane. A more restrictedobject of the present invention therefore is to enable the use at highwelding currents of electrodes having coatings which are predominantlyrutile in composition.

According to a more restricted aspect of the present invention, a methodof electric arc welding ferrous material comprises establishing anelectric are between a workpiece of said material and a coated electrodehaving a core of ferrous material provided with a bonded coating of lowhydrogen content comprising deoxidising and fluxing material andcontaining basic and rutile electrode covering materials, as hereindefined, the weight of rutile material being at least 50% greater thanthe weight of basic material, and shielding the arc and the welding zonefrom the atmosphere during welding by a shield of a gas consistingessentially of carbon dioxide, said coating acting as a barrier betweenthe shielding gas and the core, and the materials of said corefunctioning both to limit oxidation of the weld metal by the shieldinggas and to produce a layer of slag on the deposited weld metal. Weprefer the coating to contain between 65% and 20% by weight of rutilematerial.

The term basic is used herein as commonly applied to electrodecoverings. For example calcium carbonate in one of its various forms,for instance, magnesium carbonate and other carbonates, calcium fluorideand other metal fluorides and mixtures of fluorides, for examplecryolite, are basic in the accepted meaning of this term. Such materialsare included in the coverings of Class 6 electrodes of British StandardNo. 1719. In the art of manufacturing arc welding electrodes, such basicmaterials are contrasted with predominantly rutile materials whichconsist of oxides of titanium or minerals such for instance as ilmenitewhich contain a large proportion of titanium dioxide in association withother compounds. As zirconium silicate may be used in partialreplacement of the oxides of titanium this material should be consideredas a rutile material for the purpose of the present specification whenused together with oxides of titanium in the coating.

A further more restricted object of the present invention is to overcomesome of the disadvantages of electrodes having coatings of the lowhydrogen type containing a high proportion of basic material. Thus wehave found that if shielding gas consisting essentially of carbondioxide is used in conjunction with such electrodes there is a reductionin the porosity which tends to occur with such electrodes when heavydeposits are made in one or more passes. In addition there is lesstendency for porosity to occur at the beginning of a weld seam, and itis not so necessary to maintain a short are during welding in order toavoid long-arc porosity.

This type of porosity is aggravated as increasing alloying additions aremade to the coating, but we have found that this tendency isconsiderably reduced when a shielding gas consisting essentially ofcarbon dioxide is used in conjunction with such electrodes.

According to a further more restricted aspect of the present invention,a method of electric arc welding ferrous material comprises establishingan electric arc between a workpiece of said material and a coatedelectrode having a core provided with a low hydrogen, bonded electrodecoating containing between 15 and 60 parts by weight of basic material,between 10 and 30 parts by weight of felspar, and ferro-alloys between15 and 20 parts by weight, and in conjunction with the coated electrodesupplying from a source other than the electrode a gas consistingessentially of carbon dioxide to shield the arc and the welding zonefrom the atmosphere during welding.

It will be noted that the above mentioned range of coating compositionsincludes compositions containing approximately equal proportions ofbasic material, such as fluorspar, and rutile. The range also includescoating compositions having larger and smaller proportions of basic torutile materials than this.

The present invention also includes coated welding electrodes intendedfor welding in accordance with these methods, these electrodescomprising a core wire surrounded by a flux coating of the low hydrogentype. After the coating composition has been applied to the core wire itis necessary that the coated electrode should be baked at a sufiicientlyhigh temperature to drive off free water which may be contained insilicate or other binders or in the minerals contained in the coatingcomposition. The elimination of such water substantially reduces thehydrogen content of the coating composition and hence of the depositedWeld metal.

This invention is especially applicable to coilable continuouselectrodes intended for automatic or semi-automatic welding. It shouldbe noted however that short lengths of welding electrode according tothe invention may be coupled end to end to form a continuous electrode.

With flux-coated continuous electrodes it is necessary to conductelectric current from a contact member or members to the core wire asthe electrode moves through a welding head. The contact with the corewire can, if desired, be made by one or more knife edges which penetratethrough the coating as the electrode passes through the welding head butpreferably the electrode is provided with a layer or layers of windingwire or wires in electrical contact with the core. The winding wire, orthe outer winding wire where more than one layer is present, is exposedthrough the flux coating for contact with a contact member or members asthe electrode passes through a welding head. A form of construction ofmesh wound electrode as disclosed in the specification of United StatesPatent No. 2,432,048 is especially suitable, but other constructionshaving one or more layers of winding wires each consisting of one ormore wires can be employed. The winding wires also facilitate retentionof the coating composition on the electrode.

One construction of welding electrode of this type is illustrated in theaccompanying drawing which shows diagrammatically the electrode beingused to deposit a layer of weld metal on a workpiece by the method ofthe present invention.

Referring to the drawing, a continuous welding electrode consists of acore wire 1 surrounded by and in electrical contact with a wire meshconsisting of an inner layer formed by four parallel wires 2, 3, 4 and 5wound helically about the core wire in a clockwise sense and an outerlayer formed by four other parallel wires 6, 7, 8 and 9 wound helicallyabout the inner layer in an anti-clockwise sense. The wires 6, 7, 8 and9 extend to the surface of the electrode and are in electrical contactwith the wires 2, 3, 4 and 5. The interstices between the wires of thetwo layers of mesh are filled with a coating material Till thecomposition of which conforms with one of the examples set out below.The coating composition includes deoxidising and fluxing materials, andmay contain metal powders, such as iron powder,

A and a small proportion of material such as clay to facilitateextrusion of the coating composition.

The welding electrode is arranged to be fed continuously by conventionalmeans not shown through a nozzle 22 towards a workpiece 11, andconventional contact means not shown but arranged to contact the outerwires 6, 7, 8 and 9 are provided for feeding electric current to thewelding electrode just above the nozzle 22 through the mesh to the corewire 1.

In operation an arc is struck between the welding electrode and theworkpiece 11, and the welding electrode is fed continuously through thenozzle 22 towards the workpiece 11 to deposit a layer 14 of weld metalof the desired composition. Carbon dioxide is fed around the electrodethrough the nozzle 22 towards the workpiece 11 to flow around thewelding electrode and shield the welding are as indicated by the arrows.The flowing stream of shielding gas also provides protection for thewelding zone from the surrounding atmosphere in the vicinity of the arc.The slag forming materials contained in the coating form a protectivelayer 15 on the top of the deposited weld metal 14, protecting thelatter from contact with the atmosphere during cooling. By the use ofone of the coating compositions specified in the examples below inconjunction with carbon dioxide shielding, very stable weldingconditions are obtained together with smooth weld finish. Additionally,where the coating composition contains a substantial proportion ofrutile, the method results in a slag deposit 15 which is easilydetachable.

It will be appreciated that the construction of electrode used inpractising the method of the present invention may be of any suitablekind. The winding Wires, 2, 3, 4, 5, 6, 7, 8 and 9 may, for example, beomitted from the electrode shown in the drawing so that the electrodeconsists of a core wire 1 having a coating 10.

A number of examples of welding electrodes and coating compositions foruse in practising the method of the present invention will now bedescribed by way of example. In each case the electrode should be bakedat a sufliciently high temperature substantially to dehydrate thecoating if weld metal having the best mechanical properties is to bedeposited.

Electrodes having a substantially larger proportion of rutile materialthan basic material, say or more, are described in Examples 1 to 11, andthese electrodes are particularly suited for use out of the flatposition, in the horizontal-vertical fillet position for example, athigh welding currents in conjunction with a separately supplied shieldof carbon dioxide. The remaining examples relate to electrodes havingcoatings of a more basic character. The use of these electrodes in conjunction with a flowing shield of carbon dioxide provides operationaladvantages not obtained when known basic electrodes are used in theconventional manner.

EXAMPLE 1 A welding electrode as described above with reference to theaccompanying drawing has a core wire 1 and two layers of wires, 2, 1i,4, 5, 6, 7, 8 and 9, all of mild steel. The coating composition 10pressed into the intersticial spaces between the wires comprises a majorproportion of rutile material and a minor proportion of basic material.The rutile material constitutes between 65% and 20% by wei ht of thecomposition and calcium fluoride (fluorspar) between 0.5% and 20% byweight. The composition also contains deoxidising materials, such forexample as ferro-alloys, to an extent between 10% and 30% by weight. Thecomposition can also include a slag-forming material such as felspar upto 30% by weight, and if desired metal powder, such as iron powder, maybe added to increase the bulk of the metal contained in the electrode,so that it bears a suitable relationship to the amount of the rutile,basic and other materials con-.

tained in the coating composition. Such an electrode may be used for thewelding of mild steels or low alloy steels.

EXAMPLE 2 A welding electrode generally as described in Example 1 abovehas a coating whose content of rutile material is between 50% and 30%,while the fluoride content is between 1% and EXAMPLE 3 A weldingelectrode having a core wire which may, if desired, be provided with asurrounding wire mesh, is coated with a composition containing thefollowing ingredients:

Percent by weight Rutile 45 Fluorspar 5 Felspar Perm-manganese 16 Ironpowder 18.5 Bentonite clay 0.5

The purpose of the clay addition is to facilitate the ex trusionoperation by which the coating composition is applied to the electrode.The coating is baked at a temperature high enough substantially todehydrate the coatmg.

We have found that weld metal deposited under a carbon dioxide shield byan electrode in accordance with Example 3 has mechanical properties,elongation in particular, which are comparable with those obtained usingan electrode with a predominantly basic covering and similar currentdensity, but without carbon dioxide shielding. The electrode inaccordance with Example 3 was however found suitable for use inhorizontal vertical fillet welding, whereas the electrode with a basiccoating was suitable only for welding in the flat position.

EXAMPLE 4 An electrode for the welding of mild steel has a mild steelcore wire surrounded by a mesh constituted by two layers of wires woundin opposite directions around the core wire. The wires forming the meshare of mild steel. In the interstices of the mesh there is held acovering predominantly of the following compositions:

Parts by weight Rutile 45-60 Fluorspar 4-12 Felspar 12-24 Perm-manganese10-20 Iron powder may be added to obtain a suitable metal/flux ratio inthe electrode.

The ferro-alloys may include up to 10 parts by weight of term-manganeseand the balance may be ferro-silicon, ferro-aluminum, ,ferro-titaniumand/ or other deoxidising ferro-alloys.

EXAMPLE 5 EXAMPLE 6 The most suitable coating composition will depend tosome extent upon the conditions under which the work is to be welded.For instance, for welding mild steel 6 at high currents of the order ofsay 800 amperes on an electrode having an 8 S.W.G. (.16 inch or 4.1 mm.)core wire in the flat position, an electrode having a mild steel corewire and mild steel wires wound about it to form a mesh may be used witha coating composition predominantly as follows:

Parts by weight Rutile 20-60 Limestone 0-20 Fluorspar 5-20 Felspar 0-30Clay a- 0-5 Ferro-alloy selected from (ferro-manganese) (ferro-silicon)(ferro-titanium) (ferro-aluminum) 2-3 0 In addition other materials suchfor instance as iron powder, ferro-chromium, nickel or copper, and ifdesired materials to stabilize the arc by increasing emissivity orionization such as carbonates of strontium or barium may also be addedto the coating composition. If desired materials such as zirconiumsilicate or ilmenite can be used in partial replacement of rutile. Ifdesired silica can be added.

EXAMPLE 6A In a typical specific example given within the scope ofExample 6 above the coating composition may be as follows:

Parts by weight In an electrode for welding mild steel in thehorizontal/ vertical fillet welding position, the core wire and anywinding wires may be of mild steel. The coating com position may bepredominantly as follows:

Parts by weight Rutile 20-65 Limestone 1-10 Fluorspar 1-8 Ferro-alloys2-3 0 Felspar 0-30 Clay 0-5 Additional materials may be added to thecoating composition as mentioned in Example 6 above.

EXAMPLE 7A A typical specific composition of coating material fallingwithin Example 7 above is as follows:

Parts by weight 47 Rutile Fluorspar 5 /2 Limestone 5 Perm-manganese 16Ferro-silicon 2 Felspar 15 (Preferably potassium) Clay EXAMPLE 8 For thewelding of a steel containing 4 to 6% chromium and 0.5% molybdenum anelectrode having a core wire of mild steel and two layers of windingwires of similar material may be coated with a composition as follows:

Parts by weight 35 An electrode for depositing weld metal containingbetween 2 and 3% of nickel may have a mild steel core wire and mildsteel winding wires as above mentioned. The core wire is coated with acomposition containing the following ingredients:

P-arts by weight Rutile 50 Fluorspar 10 Limestone 8 Felspar 12 Clay NilNickel powder 10 Perm-manganese 15 Perm-silicon 3 EXAMPLE 10 Fordepositing welding metal having a relatively high alloy content forexample 14% manganese a major part of the alloying addition may beprovided by the core wire. For example, a ferrous core wire containing14% or more manganese may be used in conjunction With winding wires ofmild steel in conjunction with coating compositions as described inExamples 6 and 7. It will be appreciated that if mild steel windingwires are used in conjunction with a core wire having approximately thecomposition of the weld metal desired it will be necessary to addalloying elements to the coating composition. The alloying element maybe term-manganese for example.

EXAMPLE 11 For welding 18% chromium 8% nickel type austenitic corrosionresisting steels an electrode may have a core wire of a ferro-al loycontaining 18% chromium and 8% nickel and inner and outer layers ofwinding wires of the same composition. Alternatively any or all of thewires may be of mild steel. The wires may include niobium. The coatingcomposition may be as follows:

Parts by weight Rutile 20-50 Fluorspar 8-20 Limestone 5-20 Felspar -10Nickel powder -10 Ferro-niobium 0-10 Ferro-chromium -25 EXAMPLE 11A In aspecific example within the scope of Example 11 the coating may be ofthe following composition:

Parts by weight Rutile 30 Fluorspar 1O Limestone 8 Felspar 5Ferro-chromium 22 Nickel powder 6 Ferro-niobium 10 It will be noted thatin the electrodes described in Examples 1 to 11 the coating contains alarge proportion of rutile which may be in the form of the mineralrutile or may be contained in minerals including major amounts oftitania. In addition it is preferred that the coating contains a minorproportion of calcium fluoride and other basic materials as hereinbeforedefined together with a substantial amount of ferro-alloys acting asdeoxidising agents. After the coating composition has been mixed withsuitable binders to form a paste it is applied to the core wire andthereafter is baked to drive off excess water thereby reducing to a lowvalue the amount of hydrogen contained in the welding electrode. Whensuch electrodes are used in conjunction with a shield of a gasconsisting essentially of carbon dioxide we have found that Welds withexcellent mechanical properties can be effected with very high currentswhich may, for example be of the order of 800 amperes applied to an 8S.W.G. (.16 inch or 4.1 mm.) electrode resulting in a current density ofabout 40,000 amperes per square inch. Not only is the permissiblecurrent density substantially higher than has previously been foundpossible with electrodes having a predominantly rutile coating but also,despite the high current density, the weld metal has been found to befree from porosity and fissuring which may be caused by hydrogendissolved in the weld metal.

We have found that using electrodes in accordance with Examples 1 to 11there is produced during welding appreciably less fume and that the fumeis less objectionable to the welding operator than the fume produced bytypical basic electrodes, the coating of which may contain acomparatively large proportion of fiuorspar. A further advantage ofthese electrodes is that they can be used for welding out of the flatposition, in the horizontal/vertical fillet position for exam le.

EXAMPLE 12 Parts by weight Rutile 50-30 Limestone 0-15 Fluorspar 5-20Felspar 10-25 Ferro-alloys 15-20 Iron powder may be added to obtain asuitable metal/flux ratio in the electrode. The ferro-alloys may includeup to 15 parts by weight of ferro-manganese and the balance may beferro-silicon, ferro-aluminum, ferrotitanium and/or other deoxidisingferro-alloys.

EXAMPLE 12A In an electrode within the scope of Example 12 above, thecoating contains the following ingredients:

Parts by weight 0 Rutile 4 Limestone 10 Fluorspar 15 Felspar 15Ferro-alloys 18 The ferro-alloys may comprise ferro-manganese 15 partsby weight and ferro-silicon 3 parts by weight. If desired, some of theferro-silicon can be replaced by ferrotitanium and/ or ferro-aluminum.

EXAMPLE 13 An electrode intended for the welding of mild steel has amild steel core wire surrounded by a wire mesh consisting of two layersof mild steel wires wound in g "opposite directions. The layers formingthe mesh may have one or more wires in each layer. The interstices ofthe mesh are filled with a coating having the following composition:

Parts by weight Rutile 30-0 Fluorspar L 20-40 Limestone -10 Felspar 0-30Ferro-alloys -30 Bentonite clay 0-5 The ferro-alloys compriseferro-manganese 10 to 20 parts by weight and 0 to 10 parts by weight ofother ferro-alloy deoxidising agents such, for example, as ferrosilicon,ferro-titanium and ferro-aluminum.

EXAMPLE 13A In an electrode in accordance with Example 13 thecomposition of the coating may lie within the following range:

Parts by weight Rutile 30-20 Fluorspar 25-30 Limestone 0-10 Felspar20-30 Perm-manganese -20 Ferro-silicon 0-3 Bentonite clay O-2 EXAMPLE1313 In an electrode in accordance with Examples 13 and 13A the coatingmay have the following composition:

Parts by weight Rutile Fluorsp-ar 20 Limestone 10 Felspar 30 Low-carbonferro-man ganese 18 Ferro-silicon 1 Bentonite 1 EXAMPLE 14 An electrodeintended for the welding of mild steel has a mild steel core wiresurrounded by a wire mesh consisting of two layers of mild steel wireswound in opposite directions. The layers forming the mesh may have oneor more wires in each layer. The interstices of the mesh are filled witha coating having the following composition:

Parts by weight Fluorspar 40-60 Limestone 0-10 Felspar 20-40Ferro-alloys 10-30 Bentonite clay 0-5 Where both fluorspar and limestoneare used the upper limit for these two ingredients taken together is 60parts by weight.

The ferro-alloys comprise ferro-manganese 10 to 20 parts by weight and 0to 10 parts by weight of other ferroalloy deoxidising agents such, forexample, as ferro-silicon, ferro-titanium and ferro-aluminum.

EXAMPLE 14A The coating composition in an electrode in accordance withExample 14 may have a composition falling within the following ranges:

Parts by weight Fluorspar 45-55 Limestone 0-10 Felspar -35Perm-manganese 15-20 Ferro-silicon 0-3 Bentonite clay 0-2 '10 Where bothfluorspar and limestone are used together the upper limit for these twoingredients taken together is 60 parts by Weight.

EXAMPLE 14B A particular coating composition falling within EX- amples14 and 14A may have the following composition:

Parts by weight Fluorspar 50 Limestone 6 Felspar 20 Pontspar 6Low-carbon ferro-manganese 16 Ferro-silicon 2 Pontspar is a mineralcontaining a mixture of felspar and clay.

EXAMPLE 15 An electrode for the automatic welding of mild steel has amild steel core wire surrounded by a mesh constituted by two layers ofwires wound in opposite directions around the core wire. The wiresforming the mesh are of mild steel. In the interstices of the mesh thereis held a covering of the following composition:

Parts by Weight Rutile 10-0 Limestone 0-10 Fluorspar 40-60 Felspar 20-40Ferr c-alloys 10-20 Clay 0-5 EXAMPLE 15A In an electrode for weldingmild steel coming within the scope of Example 15 above the coating mayhave the following composition:

Parts by weight 5 Rutile Limestone 8 Fluorspar 43 Felspar 23Ferro-manganese l3 Ferro-silicon 2 Perm-aluminum 2 EXAMPLE 16 It isparticularly to be noted that for the welding of this type of steel itis necessary to ensure low-carbon content in the deposited weld metal inorder to obtain correct mechanical and metallurgical properties.

For the welding of a creep resistant steel an electrode may comprise alow-carbon mild steel core wire surrounded by a mesh constituted by twolayers of low-carbon mild steel wires wound in opposite directionsaround the core wire. In the interstices of the mesh there is held acovering of the following composition:

Parts by weight Rutile 40-20 Basic material 20-35 Felspar 10-25Ferro-alloys 15-30 Clay 0-10 At least a substantial proportion of theferro-alloys are of the low-carbon type. For example, the ferro-alloysmay include 10 to 15 parts by weight of low-carbon ferromanganese. Thebasic materials above referred to may include fluorspar if desired inadmixture with carbonates such as calcium carbonate up to 20 parts byweight of the total basic material.

EXAMPLE 16A In an electrode for welding a creep resistant steelcontaining 1% chromium and 0.5% molybdenum and coming within the scopeof Example 16 the coating may have the following composition:

Parts by weight Rutile 30 Fluorspar 25 Limestone 5 Felspar 20 Low-carbonferro-manganese 12 Low-carbon ferro-chromium 7 Perm-molybdenum 3Ferro-silicon 3 EXAMPLE 17 In an electrode for welding low carbonsteels, for example, of the types mentioned in Example 16 above, theelectrode may have a core with a surrounding mesh as described inExample 16. A more basic coating having the following composition may beused: 7

Parts by weight Rutile -20 Basic material 35-60 Felspar 20-35Ferro-alloys 15-30 Clay 0-10 EXAMPLE 17A In a specific example withinthe scope of Example 17 above the coating. may have the followingcomposition:

1; A welding electrode having a core wire of mild steel surrounded by alow hydrogen, bonded, coating having a composition within the followingranges:

Parts by weight Rutile between 50 and 30 Limestone between 0 and 15Fluorspar between and 20 Felspar between and 25 Ferro-alloys between and2. A Welding electrode for the welding of mild steel comprising aferrous core, a wire wound around and in electrical contact with thecore and extending to the surface of the electrode whereby electriccurrent may be conducted to the core, and a low hydrogen coating on thecore having the following composition by weight:

Parts Rutile 45-60 Fluorspar 4-12 Felspar 12-24 Perm-manganese 10-20 3.A method of electric arc welding ferrous material which comprisesestablishing an electric are between a workpiece of said material and acoated electrode having a core of ferrous material provided with abonded coating of low hydrogen content comprising, by weight: rutile45-60 parts; fiuorspar 4-12 parts; felspar 12-24- parts; term-manganese10-20 parts; and shielding the arc and the welding zone from theatmosphere during welding by a shield of a gas consisting essentially ofcarbon dioxide, said coating acting as a barrier between the shieldinggas and the core, and the materials of said core functioning to limitoxidation of the weld metal by the shielding gas and to produce a layerof slag on the deposited weld metal. I I V 4. A method of electric arcwelding ferrous material which comprises establishing an electric arebetween a workpiece of said material and a coated electrode having acore of ferrous material provided with a bonding coating of low hydrogencontent comprising, by weight: rutile 45%; fluorspar 5%;felspar 15%;ferro-manganese 16%; iron powder 18.5%; bentonite clay 0,5%; andshielding the arc and the welding zone from the atmosphere duringwelding by a shield of a gas consisting essentially of carbon dioxide,said coating acting as a barrier between the shielding gas and the core,and the materials of said core functioning to limit oxidation of theweld metal by the shielding gas and to produce a layer of slag on thedeposited weld metal.

5. A welding electrode comprising a core of ferrous material, at leastone wire wound around and in electrical contact with the core andextending to the surface of the electrode whereby electric current maybe conducted to the core, and a low hydrogen coating on the corecomprising, by weight: rutile 45%; fiuorspar 5%; felspar 15%;ferro-manganese 16%; iron powder 18.5%; bentonite clay 0.5%.

6. A method of electric arc welding ferrous material which comprisesestablishing an electric are between a workpiece of said material and acoated electrode having a core of ferrous material provided with abonded coating of low hydrogen content comprising, by weight: rutile20-60 parts; limestone 0-20 parts; fiuorspar 5-20 parts; felspar 0-30parts; clay 0-5 parts; ferro-alloy 2-30 parts selected from(form-manganese), (ferro-silicon), (ferro-tit-anium), (ferro-alumin'um),and shielding the arc and the welding zone from the atmosphere duringwelding by a shield of a gas consisting essentially of carbon dioxide,said coating acting as a barrier between the shielding gas and the core,and the materials of said core functioning to limit oxidation of theweld metal by the shielding gas and to produce a layer of slag on thedeposited weld metal.

7. A method of electric arc welding ferrous material which comprisesestablishing an electric are between a workpiece of said material and acoated electrode having a core of ferrous material provided with abonded coating of low hydrogen content comprising, by weight: rutile45-60 parts; fluorspar 4-12 parts; felspar 12-24 parts; ferro-manganese10-20 parts; iron powder 2-30 parts; and shielding the arc and thewelding zone from the atmosphere during welding by a shield of a gasconsisting essentially of carbon dioxide, said coating acting as abarrier between the shielding gas and the core, and the materials ofsaid core functioning both to limit oxidation of the weld metal by theshielding gas and to produce a layer of slag on the deposited weldmetal.

8. A method of electric arc welding ferrous material which comprisesestablishing an electric arc between a workpiece of said material and acoated electrode having a core of ferrous material provided with abonded coating of low hydrogen content comprising, by weight: rutile20-50 parts; fluorspar 8-20 parts; limestone 5-20 parts; felspar 0-10parts; nickel powder 5-10 parts; ferroniobium 0-10 parts; ferro-chromium10-25 parts; and shielding the arc and the welding zone from theatmosphere during welding by a shield of a gas consisting essentially ofcarbon dioxide, said coating acting as a barrier between the shieldinggas and the core, and the 13 14 materials of said core functioning tolimit oxidation of References Cited by the Examiner the weld metal bythe shielding gas and to produce 9. UNITED STATES PATENTS layer of slagon the deposited weld metal.

9 A I 2,432,048 12/1947 Stretton 219-146 welding electrode comprismg acore of ferrous 2 920181 1/1960 Rockefeller et a1 219 74 material, atleast one wire wound around and in electrical 5 2947847 8/1960 Craig eta1 contact with the core and extending to the surface of the 29519319/1960 Danhier 2v19 74 electrode whereby electric current may beconducted to 3:023:301 2/1962 Claussm 219 74 the core, and a lowhydrogen coating on the core comprising, by weight: rutile 45%;fluorspar up to 20%; RICHARD WOOD, Primary Examinerfelspar up to 30%;and a ferro-alloy of at least 2%. 10 MAX LEVY, JOSEPH TRUHE, Examiners.

1. A WELDING ELECTRODE HAVING A CORE WIRE OF MILD STEEL SURROUNDED BY ALOW HYDROGEN, BONDED, COATING HAVING A COMPOSITION WITHIN THE FOLLOWINGRANGES: